1. Field of the Invention
The present invention relates to a light emitting diode driving apparatus capable of stably controlling an output voltage supplied to a light emitting diode (LED) channel.
2. Description of the Related Art
Recently, interest in and demand for light emitting diodes (LEDs) have increased.
A device using a light emitting diode may be manufactured to have a compact form, such that it may even be used in a place in which it is difficult to install an existing electronic product. In the case in which the light emitting diode is used as a lighting device, various colors and degrees of luminance may easily be implemented therein, such that it may be used in a lighting system appropriate for an activity such as watching movies, reading books, conferencing, and the like.
In addition, the light emitting diode consumes an amount of power corresponding to approximately ⅛ of that consumed by an incandescent lamp, has a lifespan of fifty thousand to one hundred thousand hours, approximately 5 to 10 times that of an incandescent lamp, is environmentally-friendly as a mercury free light source, and may be variously implemented.
Due to these characteristics, light emitting diode lighting projects has been promoted in government-sponsored projects in many countries such as South Korea, the United States of America, Japan and Australia.
Further, in accordance with the recent development of flat panel display technology, a flat panel display has been used in automobile instrument panels as well as in smart phones, game devices, and digital cameras. In the future, a range of applications of flat panel displays will be increased to be included in devices used in everyday life such as micro-thin televisions, transparent navigation devices, and the like.
Further, in the current display market, new flat panel displays (FPDs) reflecting multimedia requirements such as a high resolution, large screen sizes and the like, have been prominent. Particularly, in the case of large displays, a consumer uptake rate of liquid crystal display (LCD) televisions has rapidly grown, such that it is expected that LCD televisions will dominate the market for televisions in view of the price and marketability thereof.
A thin film transistor liquid crystal display (TFT-LCD) is mainly used as a flat panel display.
TFT-LCDs include a backlight unit emitting light and mainly use a cold cathode fluorescent lamp (CCFL) as a back light source. However, recently, a rate of LED usage therewith has increased, due to various advantages in terms of power consumption, lifespan, environmental friendliness, and the like.
Therefore, a relatively cheap electronics system for a backlight unit power module using an LED, and an appropriate control element therefor, have been urgently demanded.
As described above, the light emitting diode, the use of which has increased, requires a driving apparatus for driving the light emitting diode. According to the related art, a switching element has been used in order to control respective LED channels to have constant current therein. However, as described in the following Related Art Document, the LED channels are configured of a plurality of LEDs connected to each other in series, such that voltage deviations occur between the LEDs. As a result, a current imbalance between the LED channels may occur, thereby causing the diode driving apparatus to have non-uniform luminance.
In order to decrease power consumption and heat generation due to the above-mentioned current imbalance, voltage applied to a switch switching an operation of the LED channel is intended to be maintained as low a level as possible within a limit in which an abnormality does not occur in an LED driving current (the switch may operate in a saturation region). However, in a state in which a duty of a PWM dimming signal is low, the voltage applied to the switch is decreased to be equal to or lower than the limit to which the switch may operate in the saturation region, such that distortion may occur in the LED driving current and the LED driving current may have an unstable state, whereby it may not be easy to control a desired level of brightness.